This invention relates to a downhole tool, and in particular to a pressure actuated downhole tool, such as a bypass tool.
In production of hydrocarbons from subsurface formations, drilling operations are typically undertaken using a drill bit mounted on the lower end of a drill string formed of sections of drill pipe which are threaded together. The drill string is rotated from the surface, and drilling fluid or xe2x80x9cmudxe2x80x9d is pumped through the string, to exit at appropriate nozzles adjacent the drill bit. The mud carries the drill cuttings away from the drilling zone and up to the surface through the annulus defined between the bore wall and the drill string. In certain circumstances, such as in non-vertical bores, the drill cuttings may collect in a section of the bore, interfering with the drilling operation and creating problems when it is desired to remove the drill string from the bore.
To counter this difficulty, it is known to provide bypass tools in the drill string, which tools may be configured to allow drilling mud to pass directly from the drill string bore to the annulus, without circulating through the drill bit. A typical bypass tool defines ports in the tool body which are initially closed by an axially movable sleeve. However, the sleeve is mounted to the tool body such that elevated pressure, acting on a ball which has been dropped down the drill string to engage the sleeve, causes the sleeve to move and uncover the ports, allowing direct fluid communication between the string bore and the annulus. Most existing bypass tools cannot be re-closed after the sleeve has been moved to the open position and thus must be raised to the surface to allow resetting.
In a typical drilling operation, the pressure of the drilling mud will be subject to variations as, for example, new drill pipe sections are added to the string, such that a fluid bypass tool that incorporated a freely reciprocally movable pressure sensitive sleeve would be subject to continual opening and closing, which would prove inconvenient and create delays in the drilling operation: if the drilling operation necessitated that the bypass tool was closed, it might be necessary to cycle the drilling mud pressure to close the tool before the drilling operation could commence.
It is among the objectives of embodiments of the present invention to provide a pressure actuated bypass tool which obviates or mitigates this disadvantage.
It is a further objective of the present invention to provide a fluid pressure actuated downhole tool having a plurality of operative configurations.
According to the present invention there is provided a downhole tool, the tool comprising:
a body;
a fluid pressure actuated member axially movable relative to the body;
a tool function member which is not responsive to fluid pressure and is axially movable relative to the body to an operative position; and
means for selectively coupling the fluid pressure actuated member to the tool function member to permit movement of said tool function member to the operative position on application of pressure to the fluid pressure actuated member.
According to another aspect of the present invention there is provided a method of remotely activating a downhole tool, the method comprising:
providing a downhole tool comprising a body, a fluid pressure actuated member axially movable relative to the body and a tool function member which is not responsive to fluid pressure and is axially movable relative to the body;
selectively coupling the fluid pressure actuated member to the tool function member;
applying fluid pressure to said fluid pressure actuated member to move the members axially relative to the body, thereby moving the tool function member to an operative position.
The provision of the selective coupling means between the fluid pressure actuated member and the tool function member permits the pressure in the tool to be varied or cycled without the tool functioning. Thus, in use, the pressure cycles which are typically encountered during the course of, for example, a drilling operation, will not necessarily result in functioning of the tool, which otherwise may create inconvenience and delay.
Preferably, in a first configuration said coupling means permits axial movement of the fluid pressure actuated member substantially independently of the tool function member, and in a second configuration axial movement of the fluid pressure actuated means may result in corresponding axial movement of the tool function member.
Preferably also, one or both of the fluid pressure actuated member and the tool function member are sleeves.
Preferably also, the body is tubular and defines a bore and in the operative position the tool function member permits fluid communication between the bore and the exterior of the body, that is the tool is a fluid bypass tool. In this embodiment, the tool function member may define apertures for selectively providing fluid communication with apertures defined in the body wall. Most preferably, the tool permits fluid bypass when the apertures are aligned. The fluid pressure actuated member may also define slots or apertures.
Preferably also, both of the fluid pressure actuated member and the tool function member are biassed towards a first position, most preferably by respective springs, and application of fluid pressure tends to move one or both of the members towards a second position against the action of the respective biassing member. Most preferably, the tool function member is biassed towards the first position by a biassing means which only permits movement of the member when the member is subject to a predetermined force from the fluid pressure actuated member.
Preferably also, the fluid pressure actuated member is flow responsive. Most preferably, the member defines a flow restriction such that flow of fluid through the body above a predetermined flowrate creates a pressure differential across the restriction sufficient to move the member axially relative to the body. In an alternative embodiment, the fluid pressure actuated member may be responsive to differential pressure between the tool interior and exterior.
In one embodiment, the coupling means comprises a track and follower arrangement configurable to restrict relative movement between the fluid pressure actuated member and the tool function member. The coupling means may further comprise an arrangement to selectively restrict movement of the fluid pressure actuated member on the tool function member relative to the body, which arrangement may comprise a further track and follower.
In another embodiment, the coupling means comprises a link or coupling between the fluid actuated member and the tool function member such that the movement of the fluid actuated member results in movement of the tool function member. The coupling may initially be in a non-coupling configuration allowing movement of the fluid actuated member independently of the tool function member: the coupling means may be controlled by a time sensitive actuator, which is adapted to move the coupling from a non-coupling configuration to a coupling configuration if, for example, the mud pumps are turned off and on within a predetermined interval or turned on, off and on within a predetermined interval, or indeed any sequence of mud pump activation and de-activation within a predetermined interval. Subsequently, the coupling may be returned to a non-coupling configuration. In other embodiments, the coupling means may be controlled by pressure pulses, radio signals, electrical signals or other forms of signals transmitted from the surface.
According to a further aspect of the present invention there is provided a downhole tool, the tool comprising:
a body;
a tool function member axially movable relative to the body from an initial position to an operative position;
first means responsive to a first force for permitting movement of the tool function member from the initial position to an intermediate position; and
second means responsive to a higher second force for selectively permitting movement of the tool function member from the initial position to the operative position.
This aspect of the present invention fluid provides a tool having at least three possible configurations. Embodiments of the invention may include three or more means, with a corresponding increase in the number of available intermediate positions, some or all of which may serve a function.
Preferably, the tool function member is fluid pressure actuated and the first means is responsive to a first fluid pressure force and the second means is responsive to a higher second fluid pressure force. The fluid pressure forces are preferably flow induced. The tool function member may be operatively associated with a flow restriction, which flow restriction may be fixed, or may be variable.
Preferably also, the first and second means are two or more springs, for example a pair of springs, a lower rated first spring permitting movement of the member to the intermediate position and a higher rated or pre-tensioned second spring which only permits movement to the operative position, or an alternative intermediate position, on application of the higher second fluid pressure force. In this manner the tool may, for example, be cycled while experiencing a lower first fluid pressure force without the tool function member becoming operative, and only when the tool experiences the higher second fluid pressure force does the tool function member become operative.
The tool function member may be a single member, such as a sleeve, or may be in two or more parts, coupled by appropriate means for selectively coupling the parts.
Preferably also, the tool function member defines a through bore.
The tool may be a fluid bypass tool, and in the operative position the tool function member permits fluid flow from the tool bore to a surrounding annulus.
According to another aspect of the present invention there is provided a downhole tool comprising:
a body;
a tool function member axially movable relative to the body; and
a fluid pressure actuated member operatively associated with the tool function member and including restriction means for restricting fluid flow through the body, said restriction means being movable between a first configuration, in which said means presents a minimal flow restriction, and a flow restricting second configuration, whereby in said second configuration said means facilitates movement of the fluid actuated member and actuation of said tool function member.
This aspect of the invention facilitates operation of fluid pressure actuated tools, in that the restriction means may be configured to restrict fluid flow and thus allow a relatively modest fluid flowrate to create a significant fluid pressure force. When it is not desired to actuate the member the restriction means is positioned in the first configuration, and thus does not create a significant restriction or barrier to flow through or past the tool.
Preferably, the restriction means includes one or more flaps which may be selectively extended and retracted. Most preferably, in a first configuration the flaps extend radially inwardly to restrict flow through a tool bore.